A general manual wheelchair of the prior art has a pair of casters which are installed in a front section of a chair body to function as front wheels, and rear wheels which are powered to drive the wheelchair. When a force is applied to steering shafts, the advancing direction of the casters is altered by the rotational force on a radius of rotation defined by the distance between a point on the ground contacted by the each caster and each of the steering shafts so as to facilitate steering even under a relatively small amount of force. On the other hand, when the casters butt into a step side higher than the radius of the caster, a reactive force acts on the caster wheels with a magnitude equal to the advancing force of the wheelchair to interrupt advance of the wheelchair. The wheelchair tends to have small caster wheels to reduce unbalance during climbing up hills. Then, however, the small caster makes it difficult to climb up even small steps on a road. Further, when a user detaches a hand from a drive wheel in order to give another stroke to the drive wheel during uphill climbing, the wheel tends to unbalance rearward. While downhill drive requires successive braking, a wheel contact-type brake system of the prior art hardly allows a good apply of the braking force during the movement of the wheelchair, thereby users palms can be injured.
In the meantime, a wheelchair which has electric power and/or manual drive system and the driver is allowed to be isolated without any assistant person, it is required to be equipped with clutches operated by the driver which enables disengaging the auxiliary power source in order to idle the drive wheel for manual drive for safety concern.